1. Field of the Invention
The invention relates to a method for controlling a test bench for an internal combustion engine connected on the drive-side to a dynamometer brake intended as a drive engine of a vehicle whereby a vehicle model and a driving profile for the vehicle are preset through a test bench computer, and whereby the internal combustion engine runs through the same operating points as it would run during the preset driving cycle corresponding to the vehicle model and the set point defaults of the control units of the internal combustion engine and the dynamometric brake as determined by the test bench design.
2. The Prior Art
Methods of the aforementioned type are known in the art and they are primarily (but not exclusively) used in the motor vehicle industry to be able to perform realistic tests of the internal combustion engine prior to its installation into the vehicle. The design of a corresponding test bench is diagrammatically illustrated in FIG. 1. The internal combustion engine 1 is connected on the drive-side to a dynamometric brake 2 and is provided with a device 3 controlling the same, generally called an ECU (engine control unit). In addition, there is a test bench computer 5 connected, which has its own control systems 6 to control the corresponding actuators on the internal combustion engine and to control the operating point of the dynamometric brake 2, whereby the computer acquires or computes the most important operating variables of the internal combustion engine 1 from the corresponding measuring units. The individual control systems 6 of the test bench computer 5 are in the rule set up as secondary control units which keep the output of a given actuator equal to the value of a corresponding set point. Set points are mostly determined by the user, e.g., in the form of a default of RPM (n) and torque (M) or pedal valuator position (α); however, they can be pre-stored or calculated by another program. Furthermore, such a test bench can also include a transmission 4 and/or a clutch 7.
Such test bench designs are used in the present case to test the behavior of the internal combustion engine in case of its employment in a vehicle prior to its installation. It is important in such a case that the internal combustion engine 1 is operated corresponding to the intended use. This is primarily specified by vehicle parameters and by a driving profile 8, which must be kept within certain limits. This requires, among other things, the simulation of control variables in the manner in which an operator experienced in roll dynamometer operations would preset control variables. This can no longer be preset by the user since it requires a corresponding computation specification 9 that estimates, among other things, the virtual speed of the vehicle to be driven by the internal combustion engine and whose operation reacts exactly the same as an experienced driver would do. The computation specification used for the simulation of driver behavior can be designated as driver model or driver control unit since a driver operates in actuality like a control unit. The dynamometric brake 2 must also bias the internal combustion engine 1 with the load moment that corresponds to the load on the internal combustion engine in an actual vehicle.
To achieve a realistic simulation of driving conditions, a costly synchronizing effort is necessary according to the current state-of-the-art of test benches of this type whereby the synchronizing effort has as its goal to repeat the test run over and over and to synchronize the parameters of the driver model and also that of the test bench control units after each test run until such a time when the result becomes satisfactory in total. According to current art, the parameters are then basically frozen and maintained during the time of the actual test.
Nevertheless, there are proposals, as for example in DE 4428818 or DE 4428815, which explicitly provide the possibility of monitoring the operational variables of the internal combustion engine during the test run and to select a control unit from a predetermined quantity or to correspondingly adapt the control unit parameters. These methods require, nevertheless, that at least the parameters for the operation of the internal combustion engine are set for the first test bench run prior to the start of taking measurements. In other words, the arrangement would have had to be sufficiently known from the beginning and a parameter set usable for the specific test bench run would have had to be determined in some way. These methods also provide possibilities to conduct the planned test run one time and to adapt the parameters to this test run.
The above-mentioned known methods have particularly the disadvantage that the determination of the parameter of the first necessary parameter set is very time-consuming and can occur only iteratively. Experienced test bench operators are necessary to be able to arrive at specific results at a reasonable time at all. In addition, in many tests, for example in cold start tests, lengthy cool-down periods are to be maintained between individual test bench runs, which then lead altogether to extremely lengthy preparation times for the actual measurements.
It is the object of the present invention to avoid the aforementioned disadvantages and to make the above-mentioned complicated pre-adjustments for a first usable parameter set unnecessary.